"Why, Uncle Philip! who ever heard of covering a thing up in hair or wool to keep off heat?" "I have heard of it, and seen it too, boys. It may seem strange, but it is true, that down and wool, and such things, are nearly as good to protect an animal from very great outward heat as they are to keep off very severe cold. When I was at Naples, in Italy, it was summer;--the climate is a very warm one.--The country people were in the habit of bringing snow into the city from Mount Vesuvius, and every morning I could see them coming in with their snow, which they sell to the rich to use for cooling things: and they kept it from melting with straw and wool. And in our own country, especially at the south, it is very common when a large lump of ice is brought to the house to be used through the day in midsummer, to wrap it up in a thick blanket until it is wanted. "But I have not yet told you of the tweezers. The moth has no jaws, like bees and wasps, so that it cannot pull off these hairs as the bee would; but, as I told you, it performs the work with its tweezers, which are placed in its tail, and are like the points of a pair of sugar-tongs. The insects, too, will use them very rapidly, and pull off a little of the down, spread the egg upon it, and then cover it with more down, and smooth it very neatly. Here are pictures of these tweezers." [Illustration: Tweezers of the brown and gold-tailed Moths, magnified.] "This is a curious instrument for the insect to have, Uncle Philip." "True, boys, but a very useful one. I will tell you, however, of another strange thing concerning moths with their tweezers; I mean the way in which they will sometimes place their eggs. The kind of moth that does this work is not exactly known, but naturalists think that the eggs are moth's eggs, because they are covered with the down, exactly like those which are known to be moth's eggs. These eggs are twisted round a branch, like the thread of a screw, or like the curled end of a corkscrew put over a small stick. Here is a picture of some of these eggs." [Illustration: Spiral group of Eggs of an unknown Moth.] "Ah, this is wonderful work indeed for a moth, Uncle Philip." "As you seem to like this, boys, I will just mention to you that there is another moth, called the lackey-moth, which winds its eggs also around a branch. They are hard, however, and not covered with any down, and are put on in the strongest possible way. If men wish to make an arch of stone, you know that the stones will be more narrow at the bottom than at the top, so that the bottom of the arch may make a small circle, and the top a larger one: thus-- [Illustration: A, Key-stone of an arch; B, Arch completed.]